< cpp‎ | types
Metaprogramming library
Type traits
Type categories
Type properties
(C++11)(until C++20)
(C++11)(deprecated in C++20)
Type trait constants
Supported operations
Relationships and property queries
Type modifications
Type transformations
(C++11)(deprecated in C++23)
(C++11)(deprecated in C++23)

(C++11)(until C++20)(C++17)
Compile-time rational arithmetic
Compile-time integer sequences
Defined in header <type_traits>
template< class T >
struct is_unbounded_array;
(since C++20)

Checks whether T is an array type of unknown bound. Provides the member constant value which is equal to true, if T is an array type of unknown bound. Otherwise, value is equal to false.

The behavior of a program that adds specializations for is_unbounded_array or is_unbounded_array_v is undefined.


[edit] Template parameters

T - a type to check

[edit] Helper variable template

template< class T >
inline constexpr bool is_unbounded_array_v = is_unbounded_array<T>::value;
(since C++20)

Inherited from std::integral_constant

Member constants

true if T is an array type of unknown bound, false otherwise
(public static member constant)

Member functions

operator bool
converts the object to bool, returns value
(public member function)
returns value
(public member function)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

[edit] Possible implementation

template<class T>
struct is_unbounded_array: std::false_type {};
template<class T>
struct is_unbounded_array<T[]> : std::true_type {};

[edit] Notes

Feature-test macro

[edit] Example

#include <iostream>
#include <type_traits>
#define OUT(...) std::cout << #__VA_ARGS__ << " : " << __VA_ARGS__ << '\n'
class A {};
int main()
    std::cout << std::boolalpha;
    OUT( std::is_unbounded_array_v<A> );
    OUT( std::is_unbounded_array_v<A[]> );
    OUT( std::is_unbounded_array_v<A[3]> );
    OUT( std::is_unbounded_array_v<float> );
    OUT( std::is_unbounded_array_v<int> );
    OUT( std::is_unbounded_array_v<int[]> );
    OUT( std::is_unbounded_array_v<int[3]> );


std::is_unbounded_array_v<A> : false
std::is_unbounded_array_v<A[]> : true
std::is_unbounded_array_v<A[3]> : false
std::is_unbounded_array_v<float> : false
std::is_unbounded_array_v<int> : false
std::is_unbounded_array_v<int[]> : true
std::is_unbounded_array_v<int[3]> : false

[edit] See also

checks if a type is an array type
(class template) [edit]
checks if a type is an array type of known bound
(class template) [edit]
obtains the size of an array type along a specified dimension
(class template) [edit]